Does anyone know if an e60 M5 (or maybe even a previous gen M6) wheel will fit? They can be had fairly cheap online.

Good question! I happen to like the stock 19" rims from both the E60 and F10, they are fairly similar. Did the E60 have identical brakes to the F10? It's certainly a tight fit brake clearance wise on the F10. Maybe one of the shops who have both cars in for work could do a quick test for us?